Invading the Mediterranean: Pollination, and competitive ability of the alien plant Solanum elaeagnifolium in its native habitats in Arizona

Abstract:

Solanum elaeagnifolium is a plant species native from the southwestern US to Central and South America. It is a widespread alien in several regions of the Old World, and is considered a pest throughout the Mediterranean. It is mainly associated with disturbed lands (e.g. intensively cultivated, ploughed, and irrigated agricultural fields). It is well-adapted for dispersal both through vegetative growth and seed movements. The research focus within the European project ALARM is to study how pollination biology contributes to the invasiveness of this species. As a first step, we studied its pollination ecology and competitive ability in its native habitat in southeastern Arizona during 2006. In Arizona, Solanum flowers throughout the summer and is buzz-pollinated by bees belonging to similar guilds as those associated with it in Mediterranean regions. We explored whether Solanum is pollen-limited due to competition imposed by co-flowering species during the monsoon rain season, and whether the agricultural management regime affects success via sexual vs. vegetative reproduction. We found that in the wild, Solanum is only minimally pollen-limited due to competition with four different co-flowering species. Its seed set, however, clearly depends on the agricultural management regime, with individuals in intensively managed fields (i.e., irrigated, ploughed) investing very little in sexual reproduction compared to wild populations. These results add significantly to our understanding of the invasiveness of this species both in America and in the Mediterranean.